This may be an unpopular one but: in 6.0.5 or whatever (before 6.1 patch, but not like, release week 6.0), apartments that haven't been entered in 3+ years should be demolished. Apartments were added in...3.4? That would give them some wiggle room to come in for the latest expansion if the hot new thing is what's needed. Honestly, even demolishing them sometime soon probably wouldn't be a big deal.

By no means am I suggesting that apartments should get auto-demolished every 45, 90, or even every few months, but there are some apartments that have no doubt gone unused since they were released five years ago.